[SPOILER ALERT] Attack on Titan season 4 took a much darker turn, compared to previous seasons of the series. The struggle to survive in a Titan-infested world and reclaiming their land takes a backseat as the truth of the world is revealed, and politics between nations takes over the center stage.
Eren Jaeger is thrown in the thick of it all, even more so than before, due to his possession of the Founding Titan.
There is still some lingering confusion among Attack on Titan fans regarding how Eren came into possession of the Founding Titan at all. The series leaves the implication hanging, letting the audience come to their own conclusions, but the clues scattered around are clear enough.
Disclaimer: Spoiler alert for Attack on Titan seasons 1 - 4!
How did Eren get the Founding Titan in Attack on Titan
Phrased in simplest terms, Eren inherited the Founding Titan from his father, Grisha Jaeger. But as one might expect, there is more to it. In season 2 of Attack on Titan, we find out through Rod Reiss and Historia telling Eren that Grisha Jaeger killed Rod Reiss's entire family and ate the holder of the Founding Titan, Freida. Thus stealing its power from the house of Reiss, who had long since passed it down generations.
But that does not explain why Grisha was able to turn into a titan in the first place, and that too, a titan apparently in control of his mental faculties, unlike pure titans.
It was in season 3 of Attack on Titan that we find more about Grisha's life in Marley, and the fact that he was, in fact, holding not only the Founding Titan but also the Attack Titan, passed on to him by Eren Kruger, one of the last remaining Eldian royalty in Marley.
So while Eren did inherit the Founding Titan from his father, he inherited the powers of not one, but two of the Nine Titans. Eren manifests the ability to control titans even in his human form when he comes into contact with the titan that ate his mother, who, again in a horrifying twist of fate, turns out to be his father's first wife, a transformed pure titan of royal lineage.
This establishes that a titan holder can manifest and use multiple titan powers. In season 4 of Attack on Titan, Eren eats the Warhammer Titan and seems confident that he would be able to use its abilities as well along with the abilities of the Attack Titan, and when the conditions are met, the Founding Titan. Ironically, it is not the Founding Titan that the show is named after, but the Attack Titan or "Shingeki no Kyojin", "Attack on Titan" being a slight mistranslation of the term.
The Founding Titan's importance in Attack on Titan
As the mystery unravels, we get a better look at the Attack on Titan universe and the constant power struggle amongst its inhabitants. 'Freedom', which was originally the central theme of the show, becomes more complicated, realistic, and inevitably bleak.
History is warped and manipulated to suit the ruling nation's needs. Sins are either exaggerated or glossed over as is convenient, and authentic narratives become rare.
Through preserved manuscripts and the handing down of memories, we learn of the origins of the Eldians, the Subjects of Ymir and the inheritance of the Founding Titan by successive generations of the royal family.
Eldians as a race have the ability to turn into pure titans when injected with harvested titan spinal fluid. The Founding Titan is one of the Nine Titans that Ymir's spirit allegedly split into, after her death.
The Founding Titan is believed to be superior to all other titans in Attack of Titan, harboring qualities that can only be used by someone of the original Eldian royal bloodline. It has abilities such as memory alteration, the ability to control pure titans by screaming, and even genetic modification.
In the wrong hands, the Founding Titan can be a formidable and highly destructive weapon in the Attack on Titan universe. And that is exactly what the nation of Marley is trying to get their hands on.
An interesting limitation of the Founding Titan is that while possessed by members of the royal family, they are bound by King Fritz's vow to renounce war. However, in the hands of Eren Jaeger, who has no royal blood in him, the King's vow is nullified.
This makes him a serious threat to the Marleyans, and even to the pacifist forces of Eldia, or as commonly known, Paradis Island.
Attack on Titan season 4 ends with the promise of an epic showdown between Eren and Reiner. In the previous three seasons of Attack on Titan, Reiner has steadily lost ground, and now with the power of the Warhammer Titan at his disposal, Eren might finally be on par with, or better than, the Armored Titan.